A breeding colony of healthy uniform marmosets of the genera Callithrix and Saguinus is being developed in an indoor-outdoor environment for utilization in biomedical research and teaching at Texas A&M University and other institutions. The aerobic and anaerobic fecal and oral microflora are being monitored, and efforts are being made to develop improved methods for detecting significant pathogens (e.g., entropathogenic Escherichia coli, Shigella sp, and Clostridium sp) and R-factor bearing organisms. A comparison of electrophoretic and immunoelectrophoretic profiles is being made between human and marmoset sera. Nitrogen compounds, nonprotein nitrogen compounds, non-nitrogenous organic compounds, vitamins, inorganic and ionic compounds, along with the hematocrit, WBC, RBC and differential blood counts are being determined to characterize a healthy animal and to identify problems before they become clinically evident.